Influence of external mirror on antireflection-coated phased-array semiconductor lasers

We have analyzed a phased-array semiconductor laser coupled to an external cavity containing a spatial filter. The results indicate that the external cavity-spatial filter combination couples the natural supermodes of the array. Thus if a single supermode were to be emitted by the antireflection-coated facet, the reflected field would couple into many supermodes of the same parity. By self-consistently modeling the laser-cavity configuration we show that substantial mode mixing occurs in practical cases and its effect is more pronounced when the coupling coefficient is small.